The Heat Transfer Characteristics of Rolling Wheel and the Characteristic Length Determining Them

2016 ◽  
Vol 138 (5) ◽  
Author(s):  
Liangbi Wang ◽  
Yongheng Zhang ◽  
Yuan Wu ◽  
Qiuwang Wang ◽  
Zhihui Yin
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Characteristic Length ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Rolling Wheel ◽  
Wheel Radius

The convective heat transfer characteristics on the surface of a rolling wheel are investigated using the naphthalene sublimation technique. Five sizes of rolling wheel are selected in the experiments. The local and average Nusselt numbers are obtained. The results reveal that if the wheel radius is used as the characteristic length, the relationship between Nusselt number and Reynolds number is dependent on the wheel radius. This indicates that the wheel radius is not the characteristic length to determine the dimensionless convective heat transfer characteristics of the rolling wheel. Thus, a newly defined characteristic length is provided. For different radii of the wheel, the relationships between Nusselt number and Reynolds number based on this length collapse into one reasonable correlation. The correlation not only enriches the insight of convective heat transfer on rolling wheel but also extends the applicability of the present experimental data.

Investigation on Heat Transfer Characteristics of Water Through Narrow Annulus

2006 ◽  
Author(s):  
Guangyao Lu ◽  
Jing Wang
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Heat Removal ◽  
Heat Transfer Characteristics ◽  
Number Range ◽  
Transfer Characteristics ◽  
Lower Reynolds Number ◽  
Axial Heat

A study is carried out to investigate the forced convective heat transfer characteristics of water through narrow annulus. For most works undertaken before were mainly concerned with the heat transfer characteristics of heat removal systems, the experiments herein are conducted to detect the heat transfer characteristics of heated fluid, as well as cooled fluid, flowing through narrow annulus. In the experiments, directions of flow include horizontal, upstream and downstream. The Reynolds number range, based on the annular hydraulic diameter, of 10 to 30,000 is covered in the experiments. During the experiments, the transitions from laminar to turbulent convective heat transfer are carefully observed. It is found that fully turbulent convective heat transfer is achieved at a lower Reynolds number in narrow annulus than that in larger tubes. When the Reynolds number is lower than 150, the heat transfer is degraded attributed to the slow flow rate and axial heat conduction. The experimental results indicate that the heat transfer characteristics of narrow annular flow are different from that of lager, more conventionally sized pipe flow. A convective heat transfer correlation is developed and the comparisons are made with the correlations of other works.

The Effects of Prandtl Numbers on Local and Average Convective Heat Transfer Characteristics in Helical Pipes

1997 ◽  
Vol 119 (3) ◽  
pp. 467-473 ◽  
Author(s):  
R. C. Xin ◽  
M. A. Ebadian
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Flow Region ◽  
304 Stainless Steel ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Prandtl Numbers ◽  
Experimental Findings

To investigate the effects of the Prandtl number and geometric parameters on the local and average convective heat transfer characteristics in helical pipes, experiments with three different fluids—air, water, and ethylene glycol—were carried out on five uniformly heated helical pipes. The test sections were made from 22.9 mm I.D. and 10.2 mm I.D. 304 stainless steel pipes. The ratios of the pipe diameter and pitch to coil diameter (d/D and b/D) ranged from 0.0267 to 0.0884 and 0.20 to 2.56, respectively. The peripheral and average, fully developed Nusselt numbers were evaluated in the experiments. Experimental findings indicate that after two turns (X > 2) the temperature distributions along the wall are almost parallel to the linear fluid bulk temperatures, and all dimensionless peripheral wall temperatures are nearly identical, implying that both the flow and temperature distribution within the helical pipes are fully developed. These results reveal that the peripheral Nusselt number varies significantly for higher Prandtl numbers and Dean numbers in the laminar flow region. A new set of empirical expressions for the average fully developed Nusselt number has therefore been regressed based on the present data and some data from previous investigations. No obvious effects of the coil pitch or torsion were observed in the scope of this investigation.

Experimental Convective Heat Transfer With Nanofluids

2008 ◽  
Author(s):  
S. Kabelac ◽  
K. B. Anoop
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Turbulent Regime ◽  
Heat Transfer Characteristics ◽  
Forced Convective Heat Transfer ◽  
Transfer Characteristics

Nanofluids are colloidal suspensions with nano-sized particles (<100nm) dispersed in a base fluid. From literature it is seen that these fluids exhibit better heat transfer characteristics. In our present work, thermal conductivity and the forced convective heat transfer coefficient of an alumina-water nanofluid is investigated. Thermal conductivity is measured by a steady state method using a Guarded Hot Plate apparatus customized for liquids. Forced convective heat transfer characteristics are evaluated with help of a test loop under constant heat flux condition. Controlled experiments under turbulent flow regime are carried out using two particle concentrations (0.5vol% and 1vol %). Experimental results show that, thermal conductivity of nanofluids increases with concentration, but the heat transfer coefficient in the turbulent regime does not exhibit any remarkable increase above measurement uncertainty.

scholarly journals Research on convective heat transfer characteristics of Fe3O4magnetic nanofluids under vertical magnetic field

2021 ◽  
pp. 151-151
Author(s):  
Ruihao Zhang ◽  
Sixian Wang ◽  
Shan Qing ◽  
Zhumei Luo ◽  
Zhang Xiaohui
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Reynolds Number ◽  
Field Strength ◽  
Convective Heat Transfer ◽  
Magnetic Field Strength ◽  
Convective Heat ◽  
Heat Transfer Characteristics ◽  
Magnetic Nanofluids ◽  
The Magnetic Field

This paper focuses on the convective heat transfer characteristics of Fe3O4 /Water magnetic nanofluids under laminar and turbulent conditions. After verifying the accuracy of the experimental apparatus, the effects of magnetic field strength, concentration, Reynolds number and temperature on the convective heat transfer coefficient have been studied. The convective heat transfer characteristics of nanofluids under laminar and turbulent flow conditions were studied in depth, and the influence of each factor on the heat transfer coefficient was analyzed by orthogonal experimental design method. Under the laminar flow conditions, the convective heat transfer of magnetic nanofluids performed best when the Reynolds number was 2000, the magnetic field strength was 600, the temperature was 30? and the concentration was 2%. And the convective heat transfer coefficient (h) increased by 3.96% than the distilled water in the same conditions. In turbulent state, the convective heat transfer of magnetic nanofluids performed the best when the Re was 6000, the magnetic field strength was 600, the temperature was 40? and the concentration was 2%. The h increased by 11.31% than the distilled water in the same Reynolds number and the magnetic field strength conditions.

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